Back planes and mid-planes are structures that are mounted on or in an enclosure inside of which multiple modular, pluggable, board-supported devices reside. Back planes and mid-planes can comprise Printed Circuit Boards (PCBs) that serve as an electrical and mechanical connection for the modular pluggable devices. One example of a modular pluggable device is a blade, such as a server blade, storage blade or a network blade.
A blade can comprise a comprehensive computing system that can include a processor, memory, network connections, and associated electronics—all mounted on a single motherboard or blade. Blades can be installed in a rack-mountable enclosure that houses multiple blades that share common resources such as cabling, power supplies, and cooling fans.
One of the problems with modular devices, such as those mentioned above, pertains to maintaining adequate airflow through the enclosure in which the blades reside so that the blades do not overheat. Specifically, blades can be mounted closely together in their enclosure in a parallel, side-by-side fashion, and can extend from the front of the enclosure towards the back of the enclosure to a connection point at a connector on either a mid-plane or back plane. Because the blades are mounted closely together and because the mid- or back plane usually extends perpendicularly to the desired direction of airflow, maintaining adequate airflow can be a challenge.
In the past, attempts have been made to improve airflow through such enclosures by reducing the height of the back or mid-plane, or by cutting holes in the back or mid-plane. By reducing the available surface area of the back or mid-plane, the routing space that is available for routing electrical connections to and between the modular devices is reduced. This, in turn, can drive the cost of the back or mid-planes higher because the back or mid-plane may require more layers in order to adequately route the electrical connections to and between the modular devices. In addition, because of the reduced routing space, higher-density connectors may be needed in order to accommodate a higher density of pins within a given area on the back or mid-plane.